More recycling not the solution to reducing aluminum’s carbon footprint

Aluminum cycle accounts for just over 1% of global greenhouse emissions.

It’s one thing to finally muster the resolve to take action to curb the effects of climate change. It’s another thing to actually get it done. One commonly discussed goal (perhaps drifting out of reach) is holding warming under 2°C, beyond which researchers say the damage adds up much more quickly. To do so, overall greenhouse gas emissions need to drop to less than half of what they were in 2000 by the year 2050. But can every source of emissions achieve that reduction?

A new analysis published in Nature Climate Change zeroes in on one significant source of emissions—the aluminum industry. In the same way that we can think about Earth and ecosystem processes like the carbon cycle or the nitrogen cycle, the paper lays out an economic aluminum cycle (with a fantastic figure). Aluminum is mined and processed, turned into raw products used in the manufacturing of goods, and ends up somewhere at the end of its useful life. The researchers modeled the cycle and the results showed that reducing emissions throughout the cycle will be tough.

The first product that comes to mind when you consider aluminum might be beverage cans, but that accounts for a pretty small piece of the pie. And while many aluminum products are effectively recycled, a fair amount of the metal still ends up in landfills. Indeed, Aluminum has become a poster child for recycling in general, since the smelting of aluminum ore is such a voracious consumer of energy.

Smelting is where the majority of the emissions are generated. Recovering pure aluminum from ore requires huge amounts of electricity, often supplied by coal-burning power plants. (Though the aluminum industry is huge in Iceland, despite its lack of ore, due to its plentiful geothermal and hydroelectric capacity.) And it all adds up—this aluminum cycle accounts for a little over one percent of global greenhouse gas emissions.

Because that process is so expensive, the industry has a strong incentive to recycle. Over half of the raw aluminum that enters the manufacturing sector comes from recycled material. Still, two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles. “Only post-consumer scrap recycling has the potential to significantly lower total energy use and emissions,” the researchers from the Norwegian University of Science and Technology write.

To project how changes to this industry could affect emissions in the future, the researchers constructed a model of the aluminum cycle, using it for nine different scenarios covering the spread of potential future changes to global aluminum demand. For each scenario, they evaluated the effectiveness of emissions-mitigation strategies such as capturing more post-consumer aluminum for recycling, making the smelting process more efficient, and using cleaner sources of energy to satisfy the remaining demand for electricity.

The 50 percent emissions reduction relative to 2000 goal was only achieved in one of the nine scenarios—the one with the lowest future demand. Technological advances simply cannot sufficiently offset the effect of increasing demand to hit that target.

In the model, long-term trends in emissions were controlled by recycling efficiency and aluminum demand, so improvements to the smelting process only had an impact in the short-term. The researchers point out that this means those improvements would have to be realized in the near future for the benefits to really outweigh the development costs. Their value depends on rapid implementation—a fact that seems likely to apply to other industries, as well.

The relationship between emissions and economic activity

A letter in the same issue of Nature Climate Change demonstrates a separate point relevant to understanding future emissions patterns. Some emissions projections make a simplifying assumption: emissions increase as GDP rises, and decrease at the same rate when GDP falls. The author, Richard York of the University of Oregon, writes, “…CO2 emissions depend not only on the size of the economy, but also on the pattern of growth and decline that led to that size.”

For an example, one needs look no further than the recent economic recession. “This may help explain in part the observation that the reduction in global CO­2 emissions in 2009 following the global financial crisis was modest compared with the increase in emissions in 2010.”

York surmises that this is at least partly due to the fact that many things purchased during times of economic growth—like cars, for example—hang around even if new purchases slow. Regardless, as GDP fluctuates in the future, emissions will keep ratcheting up.

These details—how emissions track economic output and how aluminum demand will affect efforts to reduce emissions—matter as we try to chart a future course that minimizes additional warming. Knowing the lay of the land is necessary to efficiently get from point A to point B. Doubly so when the clock is ticking.

66 Reader Comments

Some emissions projections make a simplifying assumption: emissions increase as GDP rises, and decrease at the same rate when GDP falls.

Isn't this a false choice? I mean, what about the solar and wind companies that are adding to the GDP, do they make the GDP go down because what they are doing are reducing emissions? Clearly, at least in some sense, technology matters to solving the emissions problem. Because when we finally have clean energy that's cheaper than fossil fuels, it'll all be worth it. And we won't have to decide whether to slow down the economy to emit, because renewable energy would be cheaper than fossil fuels, so the market would gravitate toward that. The only problem I can see is that fossil fuels currently have a slight subsidy...

I'm going to go out on a limb here, but it seems to me that Cash for Clunker's policy of destroying older cars that still had useful life left probably did more harm than good, when you consider the manufacturing process. Would those older cars really have pumped out as much greenhouse gasses during the remainder of their lives as was produced in the manufacture of an entirely new car that replaced it? Seems doubtful.

Not to mention the complete misunderstanding of wealth vs money that destroying useful goods shows.

I'm surprised to read, "two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles."

Doesn't that suggest reducing process scrap is a worthwhile place to focus research, even more than our consumer recycling?

I think the point was that the material that's already being recycled is 2/3 process scrap because the manufacturers are already recycling it. I don't know what percent of raw aluminum that goes into the manufacturing process comes out as part of the finished goods, but hopefully it's more than 50%. If so, then that means the smaller portion that's scrapped in manufacturing is already generating twice as much recycled material as the bigger portion that's passing through consumers before being junked.

This makes sense, because a manufacturer is likely to have relatively predictable, ongoing production of scrap aluminum, so they can just have containers where they collect it and periodically send it off to be recycled (and get paid a decent amount for it). A consumer who wants to junk a device isn't as likely to disassemble it and send the aluminum bits to a recycler.

I'm going to go out on a limb here, but it seems to me that Cash for Clunker's policy of destroying older cars that still had useful life left probably did more harm than good, when you consider the manufacturing process. Would those older cars really have pumped out as much greenhouse gasses during the remainder of their lives as was produced in the manufacture of an entirely new car that replaced it? Seems doubtful.

Not to mention the complete misunderstanding of wealth vs money that destroying useful goods shows.

I agree completely. What's worse is that it wasn't even a good economic spend. All it did is pull future demand into the present, so gains made while the policy was in place were offset by reduced demand in the future.

I actually believe the stimulus was a good idea, but it was spent on stupid, consumptive things like newer cars and repaving roads a couple years before they were due. It should have been invested in building new infrastructure which could have paid dividends in the future, such as, say, a super-intelligent dynamic power grid of tomorrow.

Can we just go back to all bottles? I always preferred glass over metal and plastic packaging.

The glass industry has its own challenges. Manufacturing glass also takes a huge amount of energy. Add to that process emissions, which are emissions from the process of melting glass itself and not from generating the power to melt it - glass, ceramics and cement all have huge process emissions.

This is not to say that I'm against more glass vs. aluminum. But I wouldn't take for granted that glass, even with recycling - and I know that tailings from other production processes make up for a vast amount of recycled glass, just as with aluminum - generates less CO2e emissions.

If consumer use of aluminum is only 11.1 megatonnes/year out of 46.3 megatonnes/year, then it stands to reason that even 100% recycling of those 11.1 megatonnes/year is only going to go so far. 9.8 megatonnes actually gets recycled, which is great, but the other three quarters of aluminum is not being used by consumers at all, so they can't recycle it.

According to the chart, only 17.9 megatonnes/year actually comes out - whether for recycling, landfill, etc. The rest of the 46.3 megatonnes/year remains in use. I'm not sure that actually makes sense. But assuming it does, that sets a limit that even with perfect recycling, 28.4 megatonnes/year would need to be smelted from ore.

I'm surprised to read, "two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles."

Doesn't that suggest reducing process scrap is a worthwhile place to focus research, even more than our consumer recycling?

I think the point was that the material that's already being recycled is 2/3 process scrap because the manufacturers are already recycling it. I don't know what percent of raw aluminum that goes into the manufacturing process comes out as part of the finished goods, but hopefully it's more than 50%. If so, then that means the smaller portion that's scrapped in manufacturing is already generating twice as much recycled material as the bigger portion that's passing through consumers before being junked.

This makes sense, because a manufacturer is likely to have relatively predictable, ongoing production of scrap aluminum, so they can just have containers where they collect it and periodically send it off to be recycled (and get paid a decent amount for it). A consumer who wants to junk a device isn't as likely to disassemble it and send the aluminum bits to a recycler.

-Kasoroth

I think penforhire's point is a fair one- but I know absolutely nothing about the technical constraints on process efficiency in minimizing scrap.

If consumer use of aluminum is only 11.1 megatonnes/year out of 46.3 megatonnes/year, then it stands to reason that even 100% recycling of those 11.1 megatonnes/year is only going to go so far. 9.8 megatonnes actually gets recycled, which is great, but the other three quarters of aluminum is not being used by consumers at all, so they can't recycle it.

According to the chart, only 17.9 megatonnes/year actually comes out - whether for recycling, landfill, etc. The rest of the 46.3 megatonnes/year remains in use. I'm not sure that actually makes sense. But assuming it does, that sets a limit that even with perfect recycling, 28.4 megatonnes/year would need to be smelted from ore.

They talk in the paper about increasing stocks-- aluminum products in use at any point in time. Aluminum products become more and more "popular", and it takes a while for that stuff to reach the end of its life and be recycled/disposed. As those stocks "mature", recycling volume will increase.

The biggest constraint on future demand is when stocks cease growing and the cycle hits an equilibrium point. They describe that as market saturation.

Smelting is where the majority of the emissions are generated. Recovering pure aluminum from ore requires huge amounts of electricity, often supplied by coal-burning power plants.

Isn't that more an indication that we need to move away from coal as a source of power?

Agreed - kind of like pointing out how electric vehicles can be environmentally unfriendly merely because of the source of their electricity. It's a fair point, but it doesn't say much about the environmental impact of the technology itself.

I'm going to go out on a limb here, but it seems to me that Cash for Clunker's policy of destroying older cars that still had useful life left probably did more harm than good, when you consider the manufacturing process. Would those older cars really have pumped out as much greenhouse gasses during the remainder of their lives as was produced in the manufacture of an entirely new car that replaced it? Seems doubtful.

Not to mention the complete misunderstanding of wealth vs money that destroying useful goods shows.

if you see it as a corrupt government handout to the auto industry it probably makes more sense. Not that they can keep you from buying a Kia so I'm not sure how effective it was even at that.

Can we just go back to all bottles? I always preferred glass over metal and plastic packaging.

The glass industry has its own challenges. Manufacturing glass also takes a huge amount of energy. Add to that process emissions, which are emissions from the process of melting glass itself and not from generating the power to melt it - glass, ceramics and cement all have huge process emissions.

This is not to say that I'm against more glass vs. aluminum. But I wouldn't take for granted that glass, even with recycling - and I know that tailings from other production processes make up for a vast amount of recycled glass, just as with aluminum - generates less CO2e emissions.

Although glass bottles can be sanitized and reused in certain cases. And, if you use Codd neck bottles, you don't even waste a cap.

I might be guilty of cursory reading but I think he article could be hugely improved with some numbers. Instead of all the holistic blabla add a couple of tables or charts with the actual data? And some of the assumptions are weird as well. Why should we need to restrict the use of Aluminium? We could use electricity from renewables as well. How about some computations how much the price of Aluminium would need to rise if we were to mandate a 50per cent renewable requirements for the creation. Which would be the other option. You know setting prices and letting the market do the rest which tends to work much better than the command and control bullshit hinted at in the last paragraphs.

I'm going to go out on a limb here, but it seems to me that Cash for Clunker's policy of destroying older cars that still had useful life left probably did more harm than good, when you consider the manufacturing process. Would those older cars really have pumped out as much greenhouse gasses during the remainder of their lives as was produced in the manufacture of an entirely new car that replaced it? Seems doubtful.

Not to mention the complete misunderstanding of wealth vs money that destroying useful goods shows.

Steel needs an energy input of 400kWh per tonne, minimum, in it's manufacture - this is the energy required to melt it. The true full energy cost is higher but not much more - let's say 600kWh/t.

A Toyota Camry V20, from 1986 has a 64kW engine on the base model and weighs 1.3 tonnes. Assuming all the weight of the car is steel (which it isn't), the energy gone into it's manufacture is 780kWh. 780/64 = 12.2 hours which is how long the car will need to be run for to produce enough energy for the manufacture of the steel it contains. The most up-to-date Camry weighs 1.5t and produces 133kW however the fuel efficiency is probably much higher, hence it will be releasing less greenhouse gases to move (which was the reason for the Cash-For-Clunkers scheme).

I work at an electric steel mill with a 66MW furnace, this is also approximately the power used by a cruising 747 plane. We can melt steel at about 2 tonnes a minute. So, on a 20-hour flight from London to Sydney, how many tonnes of steel could be melted by the energy a jumbo jet puts out?

I'm surprised to read, "two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles."

Doesn't that suggest reducing process scrap is a worthwhile place to focus research, even more than our consumer recycling?

I think the point was that the material that's already being recycled is 2/3 process scrap because the manufacturers are already recycling it. I don't know what percent of raw aluminum that goes into the manufacturing process comes out as part of the finished goods, but hopefully it's more than 50%. If so, then that means the smaller portion that's scrapped in manufacturing is already generating twice as much recycled material as the bigger portion that's passing through consumers before being junked.

This makes sense, because a manufacturer is likely to have relatively predictable, ongoing production of scrap aluminum, so they can just have containers where they collect it and periodically send it off to be recycled (and get paid a decent amount for it). A consumer who wants to junk a device isn't as likely to disassemble it and send the aluminum bits to a recycler.

-Kasoroth

I think penforhire's point is a fair one- but I know absolutely nothing about the technical constraints on process efficiency in minimizing scrap.

The figure linked in paragraph 2 really is helpful.

I can maybe add a bit here, although it's a very narrow perspective.I worked for a short time in a turning shop. I am pretty sure we had more than 2/3 of the raw aluminum coming in going out in the scrap bin and there wasn't too much you could do about that.One part e.g. was a pneumatic or hydraulic backplane that needed two dozen ridiculously precise holes. The outer size was close to a standard rectangular block, so only about 10% of the block to start with were milled away. About 20% of the remaining material was drilled away and more than 50% of the parts violated some tolerance. Other parts often had shapes where you needed a thick bar for the outer diameter and had to cut away more than half the material or hollow out big parts.Of course turn shops do not amount for a big part of the aluminum usage, because that's "high end" processing that costs a ton and is only done if you have a low amount of parts (initial cost of e.g. casting forms too high) or ones that can't be made on a bigger scale with a different process because of e.g. precision.

In that non representative scenario reducing scrap would have meant changing engineering decisions. And I unfortunately have an idea how complex it would have been for some of the things we manufactured to design them in a less scrap intensive way.

So if you think about the various ways aluminum gets processed and shaped from its raw form, there are some that are inherently producing a lot of scrap because you throw away everything between the shape of the part you want to have and a simple geometric shape that fits around it.Add some production mistakes to that and even rather efficient processes like casting can see 20% scrap material. And think about that from raw aluminum to finished part there often is more than one stage of processing and every stage inherently has a slight amount of scrap.

2/3 being scrap might sound like "whoa waste!!!", but I am pretty certain there's no easy way to tackle that, as a significant reduction would mean optimizing many different processes, including design choices.

I'm just thinking, isn't Apple manufacturing the MacBook's base out of a solid aluminum block?No discussion about Apple intended, but just think about how much of that gets milled and drilled away during the process. No other losses considered this should be way more than 2/3 already.Optimizing this specific process on a scale as large as Apples might be rather possible, but I assure you there's enough gotchas before you leave the engineering perspective.

I'm surprised to read, "two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles."

Doesn't that suggest reducing process scrap is a worthwhile place to focus research, even more than our consumer recycling?

I think the point was that the material that's already being recycled is 2/3 process scrap because the manufacturers are already recycling it. I don't know what percent of raw aluminum that goes into the manufacturing process comes out as part of the finished goods, but hopefully it's more than 50%. If so, then that means the smaller portion that's scrapped in manufacturing is already generating twice as much recycled material as the bigger portion that's passing through consumers before being junked.

This makes sense, because a manufacturer is likely to have relatively predictable, ongoing production of scrap aluminum, so they can just have containers where they collect it and periodically send it off to be recycled (and get paid a decent amount for it). A consumer who wants to junk a device isn't as likely to disassemble it and send the aluminum bits to a recycler.

-Kasoroth

I think penforhire's point is a fair one- but I know absolutely nothing about the technical constraints on process efficiency in minimizing scrap.

The figure linked in paragraph 2 really is helpful.

Maybe I'm misreading that diagram, but it looks to me like it's just showing the amounts of aluminum that go to different uses/reuses, without showing how much energy is used in the recycling process vs the original mining/smelting process. My understanding is that recycling is much more energy efficient than digging up ore and making new aluminum.

In the diagram, it looks like essentially 100% of the "semi-manufacturing" and "manufacturing scrap" is already being recycled, while post-consumer waste management is losing 8.1 Mt to "Other Repository + Landfill/incineration + Processing Loss" and only sending 9.8 Mt back for recycling (54.7% recycling). While it would be nice to not scrap as much in the first place, that may not be easy for certain types of manufacturing, and it may not be that big of a problem as long as the scrap is all being recycled.

From this quote: “Only post-consumer scrap recycling has the potential to significantly lower total energy use and emissions,” it sounds like stopping these losses of aluminum to landfills, etc (which must be replaced by additional new aluminum production from bauxite) provides the big opportunities to save energy usage.

-Kasoroth

EDIT-According to ehow.com, recycling takes only 5% as much energy as primary production. This would mean that the energy cost to replace the 8.1 Mt of unrecycled post-consumer waste would be equivalent to the energy cost of recycling 162 Mt of aluminum, which is far more than the total amount of manufacturing scrap.

From this quote: “Only post-consumer scrap recycling has the potential to significantly lower total energy use and emissions,” it sounds like stopping these losses of aluminum to landfills, etc (which must be replaced by additional new aluminum production from bauxite) provides the big opportunities to save energy usage.

The context of that quote is "The recycled aluminium from scrap already constitutes over half of the global aluminium ingot production in 2009. However, present global aluminium recycling is predominately based on pre-consumer scrap (32.8 Mt), which can reduce energy demand per unit of production but leads to a higher aluminium demand and an overall increase of emissions due to the inefficiency of forming and fabrication. Only post-..."

As long as demand is increasing, recycled post-consumer material will be insufficient and more will have to be mined, even if 100% of post-consumer material is captured. I think that's one of their main points.

Hattori, I think you're right. I was assuming a part manufacturer was considered a consumer in the 2/3rd vs. 1/3rd waste equation.

Of course, one way to reduce THAT waste is near-net-shape processing, like metal injection molding (MIM), casting, or typical 3D printers. If tooling was cheaper, through research effort, perhaps more parts would be made with less waste.

It's really sad. On the Columbia River between Oregon and Washington state, I have seen 3 if not 4 aluminum plants close in 15 years, two of which (Troutdale's Reynolds and The Dalles ex-Martin Marietta) have been completely demoed and removed. The third near the John Day Dam is in the process of being demolished. The northwest has some of the countries most abundant power / lowest power rates, and most of the power that supplied these plants were from nearby hydroelectric dams. with NO carbon footprint for power production. Yes, hydro IS renewable unlike where most of what you hear in the media says the opposite and those nice windmills just cant supply the power density of what water can. The Columbia Gorge is filled with windmills for as far as the eye can see east of The Dalles, into Pasco and Walla Walla, a real eye sore, but they are placed too far away from the greenies in Portland and Seattle; they don't see them, so it's OK.

Still, I fear that all this recycling of aluminum is going overseas (again) when it should darn right stay here.

The context of that quote is "The recycled aluminium from scrap already constitutes over half of the global aluminium ingot production in 2009. However, present global aluminium recycling is predominately based on pre-consumer scrap (32.8 Mt), which can reduce energy demand per unit of production but leads to a higher aluminium demand and an overall increase of emissions due to the inefficiency of forming and fabrication. Only post-..."

As long as demand is increasing, recycled post-consumer material will be insufficient and more will have to be mined, even if 100% of post-consumer material is captured. I think that's one of their main points.

I agree with Hattori HANZo that cutting pre-consumer scrap is probably pretty difficult, but to me it doesn't look like it would even have that much of a payback. If you look at it from an energy usage standpoint, scrap that ends up in a landfill is 100% scrapped and gone. Scrap that gets recycled (either pre- or post-consumer) is really only 5% scrapped.

Obviously if there's a demand for a net increase in the amount of "currently in use" aluminum (which seems to be the case), we'll need more mining to satisfy that demand, but from an energy waste point of view, the seemingly large amount of scrap that happens during manufacturing (as Hattori HANZo described) is not really that big of a problem since the manufacturers are already recovering about 95% of that "wasted" energy.

While more efficient collection of scrap that's currently going to landfills isn't enough to meet the growing overall demand, there's more room for gains there than there is at the point of reducing manufacturing scrap. If you magically eliminated all 32.8 Mt of manufacturing scrap with perfect manufacturing processes, you would cut demand, but you would also cut the supply of cheap recycled aluminum by almost as much (not counting the approx 2.1% lost as dross in the recycling process)

Effectively, that magical perfectly efficient manufacturing process would save you 100% of the 0.69 Mt (dross from the 32.8 Mt) + 5% of 32.8 Mt, or about the energy equivalent of 2.33 Mt of new aluminum production. Recycling half of what currently goes in landfills/etc, would save you 95% of about 4.05 Mt - 0.09 Mt lost in dross, or the energy equivalent of 3.76 Mt of new aluminum.

Basically recycling half of what currently goes in landfills/etc is significantly more effective than perfectly eliminating manufacturing scrap, but neither will eliminate the need for more mining unless demand for finished products is reduced.

Isn't MIM ending with a sintering process? My material science days are long gone, but I vaguely remember that porosity is a concern and that parts behave differently in their mechanical capabilities due to still being made of grains essentially.It might matter or not for the example of a laptop housing, but what you get is not the same as if you'd mill it from a solid piece.Another factor are the binder materials used for the sinter process. Whether this is only reducing scrap aluminum or also greener is not obvious to me.

Casting is less of a process, but more of a process family. There's dozens of varieties how to just pour liquid metal into a form and I guess there's quite some used for aluminum.Casting, afair, always has a bit of a problem with delicate shapes and when thickness varies much in a part. I'm not that versed in aluminum casting, but the cooling process should also be very important there and result in a different inner organization of the material, depending on whether it was more to the inside or more to the outside. We're back at asking if the mechanical implications matter.Another problem of most casting processes is that the roughness of the surface is high and tolerances are also.For a laptop case I highly doubt that it wouldn't be too severe an engineering limitation to have it produced in a casting process and also that casting alone would be sufficient.

In fact, the first idea I had about the MBP case was to have the rough outlines casted, then drill and mill it into shape. The question is if the scrap from the casting process is that much less than what you save by not milling it off. I know this is done for steel parts, but drilling and milling steel is considerably harder for the tools and takes longer. Aluminum is butter in comparison.

3D printers for metal are slow and expensive and the mechanical properties of the output were bad last time I heard about that. From what I know this is used for prototyping because the step from a CAD drawing to a part is very short and for extremely low volumes the cost is ok.

So yeah, whatever process you choose affects the outcome. The same part made by milling, die casting, sintering, forging or whatever else will differ in how it behaves mechanically. Also, every process you choose also limits what shapes you can create, on a microscopic and macroscopic level.As usually the more "wasteful" processes are more expensive, I doubt there is much to gain on this level.

You're right about the various issues or drawbacks to near net shape processing but it could be used more often with more technical breakthroughs (e.g. lower mold tooling cost). A funny one is how 1911 pistol purists are offended by some newer-design MIM hammers. Seem to still go bang every time...

Since we're so hot about cars here, I forgot to mention hydroforming (how Corvette frame rails are formed) as another efficient forming process. Yeah, tons of tooling and process development though.

Can we just go back to all bottles? I always preferred glass over metal and plastic packaging.

Maltz wrote:

Not to mention the complete misunderstanding of wealth vs money that destroying useful goods shows.

The various ideological mind cancers loose in the world today prevent any understanding or clarity on anything. I used to think it could be overcome some day, but I realize now it's utterly hopeless.

Glass is more recyclable than aluminum or plastic but has other issues, it's heavier by far and more fragile so you have a worse product to packaging ratio and more product wasted due to breakage. Interestingly I have seen a hybrid 'can' from Europe that had only an aluminum lid, the body is PET plastic. Interestingly invented by Owens-Illinois in the US.

(Though the aluminum industry is huge in Iceland, despite its lack of ore, due to its plentiful geothermal and hydroelectric capacity.)

The industry is very controversial in Iceland. Smelting doesn't produce much employment - about 2000 permanent jobs in the whole country, and many of those jobs are relatively low wage. Since Icelandic industry can't utilise the aluminium, the raw metal (a low cost product) is exported, leaving the country vulnerable to fluctuations in the price of aluminium.

And the industry has completely distorted the economy. The smelters use five times as much power as the rest of the Icelandic economy! It has demanded huge government help for the construction of infrastructure and gets its energy at subsidised rates. There have been persistant rumours that the companies were bribed to set up smelters in Iceland.

Last but not least, the construction of dams it has done enormous ecological damage in areas like Kárahnjúkar which cost something like $2.5 billion just before the Icelandic economy collapsed.

The Icelandic power companies are now realising that aluminium smelting isn't that great a deal and are looking towards things like hosting server farms which do less damage and offer more benefits for the host community.

A lot of y'all are *totally* missing the point. Look at the damn figure. Now look at it again. Now keep looking (Scott, you can't embed it in the story under fair use, can you? It's amazing.).

Out of ~30MT/yr total new production, only ~5MT/yr ends up in landfills. Recovering *all* aluminum into recycling (which many people have noted is *very* efficient compared to new production) leaves ~25MT/yr required new production.

The point that Scott has pointed out clearly and repeatedly in the comments is that the 30MT/yr goes primarily into *making* *new* *shit*. Growth. Jobs. New iPods. You can't, for example, recycle your right arm because you're currently using it, and probably will be for the foreseeable future.

Surely the real point here is that the only way to produce significant carbon emission reductions is by very significant lifestyle changes?

People in the green movement often talk as if social life can carry on more or less as now but with alternate technologies. We will still have aluminum drinks cans, just recycle them. We will still drive to out of town malls, or drive to our work on freeways, just in electric or hybrid cars. When there, we will still have the same choices of goods and food, its just that the lighting will be powered by turbine generated electricity.

The article is a small example of why this vision is totally unrealistic. Recycling is not going to cut it, if we are to reduce emissions from the production of goods made from aluminum. We are actually going to have to stop making and buying the things. Similarly, we are going to have to close down the auto industry and the suburbs and move to high density urban housing, walk to stores, and buy produce that is not oil intensively produced.

The required changes in lifestyle are massive, and not simply by the US, by the whole world. The criticism one makes of the green movement in regard to AGW is end and means. The means has to be commensurate with the end, and has to be shown to lead to it.

The classic example of the disconnect is not in the US but the UK. They are seriously proposing to build tens of thousands of turbines to achieve their Climate Act goals, but if they do, it will have no effect whatever on the global climate. Similarly when considering new road schemes, they oblige consideratin of the CO2 emissions effect, despite the fact that nothing they do or don't do in new road schemes is even going to affect the UK emissions picture, let alone the world climate.

I am skeptical of the need for urgent action on CO2 emissions, but am quite certain that gesture politics is not the answer if it is urgent. If it really is urgent, what is needed is huge lifestyle changes, including large movements of population and reductions in consumption. People who really believe in the urgency need to come clean about it, and get real about the implications of what they say they believe.

Isn't MIM ending with a sintering process? My material science days are long gone, but I vaguely remember that porosity is a concern and that parts behave differently in their mechanical capabilities due to still being made of grains essentially.It might matter or not for the example of a laptop housing, but what you get is not the same as if you'd mill it from a solid piece.Another factor are the binder materials used for the sinter process. Whether this is only reducing scrap aluminum or also greener is not obvious to me.

Casting is less of a process, but more of a process family. There's dozens of varieties how to just pour liquid metal into a form and I guess there's quite some used for aluminum.Casting, afair, always has a bit of a problem with delicate shapes and when thickness varies much in a part. I'm not that versed in aluminum casting, but the cooling process should also be very important there and result in a different inner organization of the material, depending on whether it was more to the inside or more to the outside. We're back at asking if the mechanical implications matter.Another problem of most casting processes is that the roughness of the surface is high and tolerances are also.For a laptop case I highly doubt that it wouldn't be too severe an engineering limitation to have it produced in a casting process and also that casting alone would be sufficient.

In fact, the first idea I had about the MBP case was to have the rough outlines casted, then drill and mill it into shape. The question is if the scrap from the casting process is that much less than what you save by not milling it off. I know this is done for steel parts, but drilling and milling steel is considerably harder for the tools and takes longer. Aluminum is butter in comparison.

3D printers for metal are slow and expensive and the mechanical properties of the output were bad last time I heard about that. From what I know this is used for prototyping because the step from a CAD drawing to a part is very short and for extremely low volumes the cost is ok.

So yeah, whatever process you choose affects the outcome. The same part made by milling, die casting, sintering, forging or whatever else will differ in how it behaves mechanically. Also, every process you choose also limits what shapes you can create, on a microscopic and macroscopic level.As usually the more "wasteful" processes are more expensive, I doubt there is much to gain on this level.

Thats exactly why more often we're seeing near-net shape castings followed by a forging step to reduce porosity from the casting, and improve the microstructure.

As for 3D printing (ALM), fairly sure the samples I've seen lately in titanium are close to wrought in mechanical properties. Look at a micrograph and you see the layers nicely but it doesn't seem to be too detrimental due to low porosity.

I think ALM long term is going to be more important as it matures, extremely low wastage (any unused powder gets blown away and used next time) and the ability to make geometries impossible with casting, forging or machining... but at the moment it is energy intensive and involves metallic powders which need inert atmospheres in most cases.

So really it comes down to clean electricity, both for ALM and aluminium manufacture. Take a look at figure 2 in the article. 65% comes from the power station, and 17% from fossil fuels burnt at the refinery.

Although glass bottles can be sanitized and reused in certain cases. And, if you use Codd neck bottles, you don't even waste a cap.

"Certain cases" could be made into "nearly all cases" if the exception cases are taxed highly enough. What's needed to drive greater container reuse is an economic incentive to standardise container sizes, so all manufacturers become obliged to take each others empties back.

Also recycling skips need to be replaced with automated container reuse returns skips with deposits credited via smart card. Charge the customer a dollar/pound/euro per container and give it them back on return, so very few are disposed of. During my childhood this approach was the norm for glass containers in the UK and this system persisted in France until at least the 1980ies.

Also in my household all crowncork beer bottles and cylindrical cork wine bottles are reused for homebrew - given the price of new glass bottles.